The present invention relates to aerosol dispensing devices, and in particular to valve assemblies that provide automatic dispensing of aerosol content at predetermined time intervals, without requiring the use of electrical power.
Aerosol cans dispense a variety of ingredients. Typically, an active is mixed with a propellant which inside the can is at least partially in a gas state, but may also be at least partially dissolved into a liquid containing active. Typical propellants are a propane/butane mix or carbon dioxide. The mixture is stored under pressure in the aerosol can. The active mixture is then sprayed by pushing down/sideways on an activator button at the top of the can that controls a release valve. For purposes of this application, the term “active chemical” is used to mean that portion of the content of the container (regardless of whether in emulsion state, single phase, or multiple phase), which is in liquid phase in the container (regardless of phase outside the container) and has a desired active such as an insect control agent (repellent or insecticide or growth regulator), fragrance, sanitizer, and/or deodorizer alone and/or mixed in a solvent, and/or mixed with a portion of the propellant.
Pressure on a valve control button is typically supplied by finger pressure. However, for fragrances, deodorizers, insecticides, and certain other actives which are sprayed directly into the air, it is sometimes desirable to periodically refresh the concentration of active in the air. While this can be done manually, there are situations where this is inconvenient. For example, when an insect repellant is being sprayed to protect a room overnight (instead of using a burnable mosquito coil), the consumer will not want to wake up in the middle of the night just to manually spray more repellant.
There a number of prior art systems for automatically distributing actives into the air at intermittent times. Most of these rely in some way on electrical power to activate or control the dispensing. Where electric power is required, the cost of the dispenser can be unnecessarily increased. Moreover, for some applications power requirements are so high that battery power is impractical. Where that is the case, the device can only be used where linkage to conventional power sources is possible.
Other systems discharge active intermittently and automatically from an aerosol can, without using electrical power. For example, U.S. Pat. No. 4,077,542 relies on a biased diaphragm to control bursts of aerosol gas at periodic intervals. See also U.S. Pat. Nos. 3,477,613 and 3,658,209. However, biased diaphragm systems have suffered from reliability problems (e.g. clogging, leakage, uneven delivery). Moreover, they sometimes do not securely attach to the aerosol can.
Moreover, the cost of some prior intermittent spray control systems makes it impractical to provide them as single use/throw away products. For some applications, consumers may prefer a completely disposable product.
However, many dispensing devices permit liquid with active to pass through a variety of narrow control passages in the valve. Over time, this can lead to clogging of the valve, and thus inconsistent operation. In U.S. Pat. No. 4,396,152 an aerosol dispensing system was proposed which separately accessed the vapor and liquid phases of the material in the container. However, this device did not achieve reliable automatic operation.
Thus, a need still exists for improved, inexpensive automated aerosol dispensers that do not require electrical power.